Comparative investigation of different systems of interior lighting

SRSJH/ UBMMIES

AT 267

Pagliarulo, V.

Comparative investigation of
different systems of

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ILLINOIS INSTITUTE OF TECHNOLOGY
PAUL V.GALVIN LIBRARY
35 WEST 33RD STREET
CHICAGO. IL 60616

A COMPARATIVE INVESTIGATION OF DIFFERENT
SYSTEMS OF INTERIOR LIGHTING

A THESIS

PRESENTED BY

V. PAGLIARULO

TO THE

PRESIDENT AND FACULTY

OF

ARMOUR INSTITUTE OF TECHNOLOGY

FOR THE DEGREE OF
BACHELOR OF SCIENCE IN ELECTRICAL ENGINEERING

HAVING COMPLETED THE PRESCRIBED COURSE OF STUDY IN

ELECTRICAL ENGINEERING
MAY. 1912

O O O O O r\0 O O O O

Page
Introduction ^

Description of room '''

Tests

2dl6d

9

Conditions of tests H

Comparison of results ^7

Group One ^^

" Tv.0 20

" Three 22

" four 24

Five , 26

" Six 27

" Seven 29

Eight 30

General conclusions 35

Data 37-39

Distribution curves

__INXRODUCTION_

o o o r\0 o o

The scot)e of this thesis is to gather and present
comparative data, on sSme recent lighting installations
in the Electrical Engineering lecture room, of Armour
Institute of Techaology.

Considering the importance that the profession of
Illuminating Engineering has recently attained, all
data gathered from researches conducted under rigidly
scientific methods, will add greatly to the development
and furtherance of the profession. In the tests, upon
which we intend to base this thesis, we propose to
fallow such methods as to iliminate, as much as it is
possible, all sources of error, and make the results of
the tests a truly valuable set of informations.

The problems with which the Illuminating Engineer
has to contend are many sided, and are influenced by
numerous factors. Foremost among these influencing
factors are the economical, the physiological, and the
psychological. The economical factor is of such magnitude
as to leave, many times, out of consideration all the
other factors. It is the most pressing from the consumer's

Doint of view, who is very much interested to see that
he gets the maxinjuin illumination with the least expen-
diture of energy. As to the physiological factor, a
prominent oculist in this city has many times asserted
that a certain theatre has been the mean of copioas rev-
enue to him on account of the archaic system of illumina-
tion. Helmholtz emphasized the fact that the effects of
illumination upon the eyes are physiological rather than
physical, therefore a prolonged strain upon the eyes,
such as may result from long exposure in a badly illu-
minated room, is apt to produce serious injury. On the
other hand, it is a fact that the illumination of a room
or hall, has a decided effect upon an individual, making
him feel cheerful or gloomy, according as the illuraina*
tion is glittering bright or subdued.

Illumination installations must also harmonize with
the surroundings. This we might put down as a general
law in Illuminatinj? Engineering. The illumination of a
ball room, of a drawing room, or of a library, are
specific problems, each one requiring a separate solu-

tion. There are other classes of service where the qual-
ity of the light, as well as the quantity, is a deciding
factor. Take for instance a dry goods store, where it is
essential that the color appearance of the goods be not
changed from their day-light appearance.

We may now inquire, what constitutes the best illu-
mination for a school lecture room ?. This question is
by no means an easy one to answer properly. And there
are, perhaps, no two illuminating experts who will answer
it in the same way, or peremptorily agree on every point.
We may start by putting down some items which are so
essential to be beyomd discussion. A lecture room, for
instance, must be as evenly illuminated as Dossible. A
room that is equally illuminated all over, undoubtedly
produces a more pleasing effect, than one which presents
dark spaces and dark corners. That this is not an
irrilevant item may be argued from the point that a
school room "per se" is not a place where a student,
speaking of the average tyoe, stays with pleasure regard-
less of the appearance. It has to be made attractive to

hirudin order that the natural adversion for the place be
mitigated. Furthermore; in places where there is a wide
variation in the brightness of objects, the observer will
suffer a depression of visual functions, and due to the
direct connection between the eyes and the brain, he is
likely to suffer also a depression of brain functions, a
reduction of his ability to learn, or pay sustained
attention.

Besides being evenly illuminated, a school room must
have enough light for every student to see clearly. It
is true that the eyes are able to adjust themselves over
a wide range of intensities, and as far as being able to
see is concerned, we can see as well in a relatively dark
room as in a brightly illuminated one, after the eyes
have been accustomed to the light conditions. But to
work in a dark room, where an effort must be made to see
clearly, means a constant strain on the optic nerve, which
eventually may lead to serious injury to the eyes,
Analizing the conditions of the students who attend e-
vening classes in the room under consideration, we find

that they are mostly young men who are amployed during
the day, and who are willing to make an extra effort to
further their education and advantages. Clearly, when
they come to classes they are not in the best physical
conditions to accrue knowledge, since the body and the
eyes are tired after working an entire day. Then, if
the additional tax is imposed of working in a room
where the eyes are strained still more, the probabilities
are that the high aims of the students are apt to end
disastrously. We do not here intend to convey the idea
that the room shall be lavishly^ or wastefully illunimated.
An illumination which shall strain the least the eyes of
the studants is what is desired. The best authorities
give a uniform illumination of 2 to 3 foot-candles as
necessary for a school lecture room.

Glare is a very undesirable phenomenon anywhere, much
more undesirable in a lecture room. It depresses the
visual functions, which, as was pointed out above, is a
decided disadvantage. Without going into a scientific
explanation of glare, let it be sufficient to say that

glare is practically due, to sources of too great intrin-
sic brilliancy within the field of view, or of too great
absolute intensity at short distance. It is recognized
among illuminating experts, that the specific brightness
of the illuminating sources within the field of view
must be kept within definite limits, under given condi-
tions, to avoid eye strain.

Another undesirable phenomenon, at least as far as a
school room is concerned, is perfect diffusion. In a
school room is imperative that there be sharp definition
of obiecti, especially during demonstrations of exper-
iments from the lecture- table, and also to give form
and solidity to surroundings.

Recapitulating what we have said, regarding the prop-
er illumination of a lecture room, we find the essential
requirements to be: An even distribution of light on the
working plane. A sufficiently high intensity on the
working plane, for each student to work without undusly
straining his eyes. There must not be any strong light
sources within the angle of vision. Perfect diffusion

must be avoided. In the present case we will endeavor to
deternitne whieh of the three lighting installations now
in the raora, more nearly apBroaches these conditions.
Since the author is in no waji connected with the concerns
which have furnished the reflectors for the installations
and is not under any oblifiation to them, perfectly
impartial conclusions will be drawn from the results
obtained from the tesff's.

DESCRIPTIOfJ OF THE RQQM _

OOOO'>0OO0

The Electrical Engineering lecture room is located
on the second floor of the main building, of Armour In-
stitute of Technology. It is 27.5 ft. long, 23 ft. wide
and 14..5 ft. high. On the east wall are four large win-
dows, provided with shades and counter shades. On the
south wall is a blackboard covering the central half
of the wall, and on the west corner is a small switch-
board panel. The west wall h^s the door near the north
corner. On each side of the door is a blackboard, and
near the south corner is a space 5 ft. square, painted

clear white, on which are projected the lantern slides.
The north wall is for the entire length covered with
blackboard 3 ft. wide. The room also contains a lecture,
desk, near the south wall, a lantern stool, a lantern
and a number of chairs. A plan view of the room is given
in figure 1.

The walls of the roora, where they are not covered with
blackboard? and other apparatus, are painted with a
yellowish-brown color. The ceiling is painted with a
mellow cream color. The room has but recently been oainted
and is in an eccellent condition for such investigation
as we propose to carry in it.

The ceiling has five outlets from which fixture are
hung. There is one center outlet, and four other outlets,
one in the center of each of the four auarter bavs>in
which the room was devided. The fixturejhave been designed
especially for this installation; so that the reflectors
may be grouped on the center fixture, or distributed on
the corner fixtures. The reflectors may also be hung
downwards or turned upwards.

There are three lighting circuits leading to the fixt-
ures, one for the center, one for the distributed fixta
ures when the reflectors are hanging downwards, and one
for the distributed fistures when the reflectors are
turned upwards. The circuits are controlled by means of
Dush botton switches, the arrangement of which is such
that only ine circuit is alive at anji one time.

__1ESTS__

O O O r\a o o

The tests will consist of finding the intensity of
illumination on the working olane. The fixtures are so
arranged, that the distance between the ceiling and the
reflectors may be varied at will. It will be possible
to determine, therefore, the distance of the reflectors
from the ceiling, which will give the best illumination
on the working plane.

Three different types of reflectors will be used in
this investigation, as fellows:

Four E-lOO reflectors, furnished by the National
X Ray 80. These reflectors will be used as an indirect

10

lighting system. The tests which we propose to carry on
these reflectors are six, tRree when the p§flectors are

grouped on the center fixture, and three when they are
distributed on the corner fixtures. A test will consist
in obtaining the light distribution on the working plane
when the reflectors are at a definite distance from the
ceiling. With the reflectors grouped on the center fixt-
ure,, the three tests will made when the rsfledtors are
3ft., 4 ft., and 5 ft., from the ceiling. With the
reflectors distributed on the coroer fixtures, the three
tests will be made having the reflectors 2 ft., 3 ft.
and 4 ft. from the ceiling.

The other type of reflectors which we will use are
four )^3445 Alba reflectors, furnished by the Macbeth-Evans
Co. On these reflectors nine tests will be made, three
when the reflectors are grouped on the center fixture,
the reflectors turned upwards, the edge of the reflectors
being 3 ft., 4 ft., and 5 ft. from the ceiling. Three
more tests will be made, with the reflectors distributed
on the corner fixtures and turned upwards, the edge of

11

the reflectors being 2 ft., 3 ft., and 4 ft. from the
ceiling. The other three tests will be made, with the
reflectors distributed on the corner fixtures and turned
downwards, tlje edge of the reflectors being 3.75 ft.
4.75 ft., and 5.75 ft. from the ceiling.

The other type of reflectors which we will investigate
is type F -150, satin finish, furnished 'Oy the Holophane
Co. The tests nerformed on these reflectors will be
essentially the same as those performed on the Alwaa
reflectors, one for one.

__GQNDITI0MS-QF_IHE_1ESIS__

O O O O p,0 o o o

Since this will be a corcoarative investigation, in
order to be fair to all concerned, the tests will be
made under identical conditions. Accordingly , four 150
watts, wire drawn filament, tungsten lamps were chosen
to light the room. These lamps were new lamps, but had;
been burned moee than 50 hours before using them in the
tests, in order to insure a nearly constant candle-pwar
for the duration of the teits. The lamps, as appears

12

from the calibration data, were of nearly the same candle
power.

The candle power of the lamps was determined in the
usual manner. In order to eliminate errors due to color
differences of the light sources, a 25 c.p. tungsten
lamp was used as a standard of comparison, this lamp
having previously been standardized with a 16 c.p. carbon
lamp standardized by the Bureau of Standards. A Luramer-
Brodhun contrast photometer screen was used to obtain tne
photoraetffic balance. In calibrating t.iie lamps to, find
the mean horizontal candle power (M.H, C.P. ), they were
rotated through a small angle about a vertical axis.
The candle power intensity all around the lamp was found
to be about the same, as is shown in tables II to IV
inclusive. Multipl:^ing the M.H..C.P, thus found, by the
reduction factor, which for these lamps is .79, as deter-
mined by the manufacturers, the M.S. C.P. was obtained.
The total lumens emitted by the lamp is, its M.S. C.P.
multiplied by 4/7'. The voltage impressed upon the lamps

13

which remained constant during the tests^ was 110 volts
as measured by a standardized Weston voltmeter. To
maintain a constant voltage across the lamrs, advantage
was taken of the use of a storage battery as a source
of power. This saved much work in correcting the test
readings for variation of voltage, which would be reauired
if the lamr>3 were lighted with power derived from the
generator, the voltage of which is subject to wide varia-
tion. Table I gives the calibration of the comparison
25 c,p. lamp. Tables II to V inclusive gives the results
of the calibration of the four cervice lamtjs.

The photometer used during the tests was a Sharp
and Millar universal ohotometer. It was calibrated to
read directly in foot candles, by Dlaciflg the test plate
exactly 4 ft, away from the filament of the standard 16
c,p. carbon lamp. That we shoud get this intensity of
illumination at that distance from the lamp is readily
apparent from a consideration of the definition of
foot candle, and the physical fact, that the intensity of
illumination varies inversely as the sauare of the dis-

14

tance from the source. Since one foot candle is the inten-
sity of light falling normally on a surface one foot
away from the source of one candle intensity, and

I
Intensity c>^ -'-:-■ — -r

d2 ■

"?' ' '7" ' '

To make the Dhotoraeter read directly, besides placing
the test plate at the proper distance from the standard
lamp, the index of the scale was placed on the 1.00
foot candle mark of the photometer scale. The voltage of
the standard lamp was adjusted to the proper value to
give 16 C.P., and the photoirieter balance was now obtained
by varying the voltage impressed on the photometer lamp
by means of a rheostat. A constant voltage was maintained
across the standard lamp by connecting it to the storage
battery. The photometer lamp was connected to 2 storage
cells in series. The pressure across the terminals of t
the photometer lamp was measured by means of a Weston
millivoltmeter.

15

The floor of the room in which the tests were made
was devided into four eaual sections. Since the lighting
fixtures are symmetrically placed, and the lamps are of
nearly the same candle power, the light survey made in
one Quarter section will be the same as that of the
other sections, with respect to the center lines of the
room. The north east section was chosen ( see fig. 1)
for no other reason than that of accessibility, and free-
dom from interference. The section chosen was subdevided
in thirty sauares 2.3 >« 2.3 ft. and a test station
located in the center of each square.

The room is one which is daily used for lecture
Durposes. During the tests, nonfof the furniture or appara-
tus which is permanently in the room was removed. The
chairs are of a dark oak color. During the tests, they were
put together on ©ne side of the room. The lecture table
the lantern stool, the floor, and the door are of a light
oak color. The ceiling is of a light cream color^and has
been but recently painted. The walls, also but recently
painted ,■ where they are not covered with blackboards, are

-1§_

of a yellowish- brown color. Twc shades v/ere used on each
window, to reduce the amount of light admitted into the
room by specular reflection. It was found, that with the
present arrangement of shades, a small amount of light
still creeps in from around the periphery of the
windoB. An attempt was made to measure the amount of
this stray light, and make the ppoper corrections in
the actual readings; but the plan had to be abandoned
on account of the impossibility of measuring this
light with any degree of accuracy, so small was its
intensity. In any case, it only introduces a very small
error varying from about ,5% in the readings taken in
the stations near the center of the room, to about i%
in the readings taken in the stations nearer the windows.
Also, since the tests were made in the afternoon, between
2 p.m. and 7 p.m., the percent of error varies from a
maximum to zero, as the evening approaches. The color of
the inner shades is of a greenish-yellow.

The plane of reference was taken^as a horizontal
plane 30 inches above the floor.

.12.

The reflectors were kept thoroughly clean during the
tests. Incidentally it was noticed, that with the Holophane
reflectors, an error of about 2b% is im.troduced by having
the reflectors covered with dust. With the X Ray reflec-
tors this erro» increases to about 35%,

On account of the many precautions taken to eliminate
errors, it is believed that the results obtained in these
tests are within 2% of actual values. The measuring
instruments, such as voltmeters and ammeters, and the
photometer, were recalibrated frequently to guard against
errors creeping in. Three readings were taken at each
station by the same observer, and in the tables the
arithmetical mean of these readings is givem.

OOOOpOOOO

All the twenty four tests performed, may be devided
in eight groups, each group embodying those tests
performed on one type of reflectors when operating at
different distances from the ceiling.

_QrfiliJ2_Qfla_: This group consists of the tests

18

performed on the XRay reflectors when placed on the center
fixture. The results of tne tests are given in tables VI
to XIX inclusive. The distribution curves for the same
group are given in figures 1 to 6 inclusive.

The characteristic features cf this group are as
follows: The intensity of illumination is high right under
the reflectors, and decreases rether rapidly as the
horizontal distance from the center of the room increases.
The variation of intensity is, however, uniform jso that
a great contrast of illumination intensities is avoided.
The intensity becomes entirely too low, for any student
to work with conifort for any length of time, about seven
feet frdiin the center of the room . The zone of usefulness
these reflectors used in this manner is, therefore, limited,
The highest intensity attained is 3.5 foot candles, right
under the fixture, as is shown in the tables and curves.
The lowest intensity is .75. foot candles, in the farthest
corners of the room.

The highest intensity is attained when the reflectors
are 2 ft, from the ceiling. At this distance, however, the

rate of decrease of the intensity, as the horizontal
distance from the center of the floor is increased, is
the greatest. Glancing at the curves for this group we
see, that the distribution curve for this test cuts the
curves of all the other tests before reaching the edge
of the floor. In our opinion, the best results ier these
reflectors are obtained when they are hung 3 ft. from
the ceiling. Though the rate of decrease of intensity,
when the reflectors are so placed, is a little higher
than when they are placed i ft. or 5 ft. from the ceiling
the intensity is also higher all along. The average inten-
sity on the working plane, being the mean of all the
thirty readings of the test stations, does not change
appreciably, as may be seen from the tables, as the
distance of the reflectors from the ceiling ie changed,
eccept when they are five feet from the ceiling, when the
average intensity falls off about 10^. The highest
operating efficiency of this group is attained, when the
reflectors are 3 ft. from the ceiling.

-2Q.

.QBQUE^TID-'. This group consists of the tests performed
on the X Ray reflectors, when distributed on the corner
fixtures. The results of these tests are given i*
t&bles X to Xn inclusive, and the distribution curves
for the same group are given in figures 7 to 12 inclusive.

The characteristic feature^of this group are as fallowa:
The intensity is good in the center of the room, and it
remains so, as the edge of the fioor is approached. The
distribution curves of this group are flat, indicating
that the rate of change of intensity as we go farther
from the center of the room, is not so high. Within the
area in which the students are seated, the intensity of
the light is sufficiently high for any student, whose
eyes are not defective, to be able to work without discom-
fort. The zone of usefulness of these reflectors when
used in this manner is large, much larger than when they
are placed on the center fixture.

The highest intensity attained is 2.5 foot candles
in the center o£ the room, as is shown in the tables
and in the distribution curves. The lowest intensity is

21

1.1 foot candles. The highest intensity is attained, when
reflectors are i ft. from the ceiling; but again, when
the reflectors are at this distance, the decrease of light
intensity, as the distance from the center of the room
is increased, is most rapid.

In our opinion, the best results are obtained with
the reflectors so used, when they are placed 3 ft. from
the ceiling. The variation of intensity is not great, any
way, as the distance between the reflectors and the
ceiling is cnanged, and the preference of placing them
3 ft. from the ceiling is merely one of appearance. The
average foot candle intensity on the working plane; that
is; the mean of the thirty readings taken in the test
stations, does not change at all, in the range of our
tests, as the distance between the refledtors and the
ceiling is changed. Whatever change there is, it is
certainly less than the experimental error. The Highest
operating efficiency of this group is attained, when
the refledtors are 2 ft. from the ceiling. The change
of efficiency* from placing the reflectors 2 ft. from the

-22_-

ceiling, to placing them 3 ft., however, is negligible
and the sacrifice may cetainly be made for the sake
of appearance,

-QEQDE.IiiBEEi This group consists of the tests
performed on the Alba reflectors, when placed on the center
fixture, turned upwards. Thus placed the reflectors act
as a semi-indirect system of illumination. The results
of the tests are given in tables XIII to XV inclusive
and the distribution curves are given in figures 13 to 17
inclusive.

The characteristic features of this |roup are as
follows; Very high intensity in the center of the room
decreasing very rapidly as the distance from the center
of the room is increased. The variation is so rapid
that the intensity near the edges of the floor is hardly
sufficient for any normal student to work with comfort.
The distribution curves are very peaked, and show very
well how high the rate of change of intensity is.
Within the area where the students s«et, the intensity
is high but variable. This is not a good feature.

-22.

permitting a considerable waite of energy by throwing
considerably more light than is desired in a limited
zone, while in other zones the light is less than suffi-
cient.

The highest intensity attained with these reflectors
used in this manner is 7.55 foot candles in the center
of the room. The lowest intensity is 1.05 foot candles.
The highest intensity is attained/ when the edge of the
reflectors is 5 ft, from the ceiling, but at this dis-
tance the rate of decrease of light intensity is also
the greatest, as the distance increases from the center
of the room.

Since within the useful zone the intensity is suffi-
ciently high, whether the reflectors are three, four, or
five feet from the ceiling, it appears to us that by
having them three feet from the ceiling is the best arrange-
ment. It is true, that at that distance the average inten-
sity is lower than if the distance was five feet, but
the appearance is better. Furthermore, with the reflect
tors placed five feet from the ceiling, they are fully

24

within the angle of view of those students who s«it in
the back roas, who thus have to suffer the objectionable
effects of glare.

there is an apprecialle change in the average foot
candke intensity , when the reflectors are placed three,
four, or five feet from the ceiling. The highest
operating efficiency of this group is attained when the
reflectors are placed 5 ft. from the ceiling,

_«QBQiJ£_£QiIEl This group consist of the tests perforrced
on the Alba reflectors, when placed on the fixtures dis-
tributed in the four bays, turned downwards. The reflec-
tors arranged in this manner act as direct system of
illumination. The results of the tests for this group
are given in tables XVI to XFIII inclusive, and the
distribution curves are given in figureft 19 tp 24 inclu-
sive.

Among the characteristic feature of this group we
note the following: The distribution is almost ideally
even, when the refledtors are no more than four feet from
the ceiling. The change of intensity from the center of

25

the room, where it is the highest, to the edge of the
floor, where it is the lowest, is first of all small, it
is, furthermore, so gradual as to be unnoticeable to the
eyes. The intensity is also higher than it is required
for a school licture room. The zone of usefulness of
these reflectors, when used as described above, embraces
the entire room. Nowhere, eccept in the^ extreme corners
the intensity is so low, as to make any normal student
uncomfortable while working.

The highest intensity attained is 4.4. foot candles
right under the lamps, the lowest intensij^y is 1.75 foot
candles in the exjbreme corners of the room. The highest
intensity is attained when the reflectors are 5. ft. 8 in.
from the ceiling. In the center of the rooD), however, the
intensity is higher when the reflectors are 4 ft. 8 in.
from the ceiling. This is due to the fixjt that in hanging
the reflectors nearer the working plane, they shield and
absorb more of the direct light coming from the incandes-
cent filament of the lamps. This is very well shown in
figures 19 to 23, where the curve of light distribution

-2g.

with the reflectors placed 5. ft. 8 in. from the ceiling
is seen to be lobed, while the other curves are smooth.

In this case again, in order to avoid the effects of

it
glare in the eyes of those students seating in the back

rows, it is more convenient to sacrifice the highest
efficiency on the altar of comfort, and place the reflec-
tors 3 ft,, 8 in. from the ceiling. The highest operating
efficiency of this group is attained, when the reflectors
are 5 ft., 3 in. from the ceiling.

GBQIi£-ElYE_# This group consists of the tests performed

on the Alba reflectors, when placed on the fixtures in the
four quarter bays, turned upwards. The reflectors
arranged in this manner act as a semi-indirect system of
illumination . The results of the tests for this group
are given in tables XIX to XXI inclusive, and the distribu-
tion curves are given in figures 25 to 30 inclusive.

The characteristic features of this group are essen-
tially the same as those of group four. The distribution
is again very even, and the rate of decrease of intensity
is negligible. The intensity is sufficiently high, being

27

well within the limits prescribed by the best authorities
on illumination. The effects of glare may also be consid-
ered as negligible, as the incandescent, filaments of the
lamps are completely shielded by the opaque reflectors.
The absence of lobed curves is a noticeable feature of
the distribution curves.

The highest intensity attained with the Alba reflec-
tors used in this manner is 3.8 foot candles in the cen-
ter of the room, and the lo«f8st intensity is 1.5 foot
candles in the extreme corners. The distance of the
reflectors from the ceiling does not af fectj'either the
average intensity of illumination on the working plane
nor the smoothness of the distribution. The most suitable
arrangement, in our opinion, is when the reflectors are
placed 4 ft, from the ceiling.

_SEQUP^SIXl This group consists of the tests performed
on the Holophane reflectors, when placed on the fixture
in the center of the room, turned upwards. The reflectors
arranged in this manner act as semi-indirect system of
illumination , The results of the tests for this group

28

are given in tables XXII to XXIV inclusive, and the
distribution curves are given in figures 31 to 36 inclusive,

In the characteristic features of this group may be
noted the following points: The intensity is very high
in the center of the room and decreases very rapidly
towards the wail. Here agiln we find an intensity unnec-
essarilj^ too high in one place, and decidedly law in
other places where we still need a high intensity. The
distance of the reflectors from the ceiling has very
little effect on the distribution of the light, or on
its intensity, as is well shown by the distribution
curves.

The highest intensity attained with these reflectors ^
4.1 foot candles in the center of the room, and the lowest
intensity is 1 foot candle in the farthest corners. With
the reflectors placed 5 ft, from the ceiling the highest
intensity is attained. The rate of change of intensity^is
also greatest^ at this distance of the reflectors from
the ceiling.

For the same reasons given in the discussion on the

29

previous groups, the reflectors, in our opinion, should
be placed three feet froic the ceiling for the best
arrangement. The operating efficiency of this group is
graatest when the reflectors are 5 ft, from the ceiling,

-CEQUE-SE^EI^^: This group consists of the tests
performed on the Holophane reflect^rrs; when placed on the
fixture in the four quarter bays, turned downwards. In
this arrangement the reflectors act as a direct system
of illumination. The results of the tests for this group
are given in tables XXV to XXVII inclusive, and the
distribution curves are given in figures 37 to 42 inclusive,

The features of this gtoup are the following: The
distribution is extremely uneven, the intensity varying
from eccessive, right under the lamps, to barely suffi-
cient around the border of the room. The high intensity
however, within the useful zone makes this arrangement
of reflectors a very commendable one. The most objec-
tionable feature of these reflectors, when used in this
manner, is the presence of glare, which is produced by ^'^
high intrinsic brilliancy of the edges of the refracting

_3Q.

prisms. With this system glare is unavoidable, no matter
how high the reflectors are placed. The contrast is so
great, between the high intrinsic brightness of the edges
of the prisms and the M»t of the surroundings, to be a
constant source of distraction to the students.

Another marked feature of the group is the appree-
ciable difference in intensity and distribution, when the
distance between the^ reflectors and the ceiling is varied.
The highest intensity, 6.6 foot candles, is obtained
when the reflectors are 5 ft. from the eeilng. The glare
effects at this distance, however, is so grejt as to make
the arrangement altogether impractical. The reflectors
should be as near the ceiling as is possible to put them
to minimize the effects of glare. The highest efficiency
is also attained when the reflectors are 5 ft., 8 in.
from the ceiling.

__QEQUE-EIQEIl This group consists of those tests
performed on the Holophane reflectors, when placed on the
fixtures in the four quarter bays, turned upwards. The
reflectors thus used constitute a semi-indirect system

-21.

of illumination. Tha results of the tests for this group
are given in tables XXVIII to XXX inclusive, and the
distribution curves are gisren in figures 43 to 48 inclusive.

Among the predominating features of this group we
note that the intensity is anywhere hardly sufficient
for the purpose. The zone of usefulness of these reflec-
tors arranged in this sanner is very, very limited
making this arrangemsnt impractical. Another very objec-
tionable feature is the predominance of glare. The
efficiency is decidedly low.

This completes the discussion on single groups. We
may now compare the features of the three types of
reflectors when operating under the same conditions.
Beginning with the arrangement when the reflectors are
grouped on the center fixture. We note that with this
arrangement any type of reflectors under tests, whether
X Ray, Alba, or Holophane,. gives a decidedly bad distribu-
tion. The X Ray reflectors, even when at their best, do
not give a sufficiently high intensity at some distance
from the center of the room to make them practical. In

our opinion, the X Ray reflectors are at a great disadvan-
tage when compared with the other reflectors. The Alba
reflectors, although giving a bad distribution, maintain
a sufficiently high intensity in any part of the room
for any student to work with comfort. Another commendable
feature of the Alba reflectors is the almost complete
absence of glare, especially if they are placed near the
ceiling. The Holophane reflectors besides the bad distribu-
tion present the objectionable feature of glare. The high
intrinsic brilliancy of the edges of the prisms is always
in evidence, no matter how near the ceiling the reflec*
tors are put. Economically the Alba reflectors have the
advantage over the other types, possessing a higher effi-
ciency. The physiological factor is also in favor of the
Alba reflectors, presenting no glare effects. The X Ray
reflectors are also commendable in this respect, because
they give a very soft light effect, free from glare or
strong contrast in wide difference of intensity of
illumination.- The objection frequently advanced against
the X Ray reflectors, as producing a gloomy and depressing

_SS-

effect upon the observer^ is certainly absent in this
case. The real objection lies in the comparatively low
efficiency of the reflectors. Had these reflectors a
little higher efficiency, which would mean a higher
average intensity of illumination on the working plane
they would surely make t^e most acceptable syst|m of
illumination . As it is, they must give way to the
Alba reflectors, at least as far as the illumination of
this room is concerned.

Analizing the comditions when the Alba and the
Holophane reflectors are ^itii placed on the four quarter
bay fixtures, turned a^wa^^, or, in other words, when
acting as a direct lighting system, we notice that the
Alba reflectors again have the advantage. The average
intensity on the working plane is higher, it is- true, with
Holophane reflectors, making them have the higher opera-
ting efficiency, but it is also true that when the effi-
ciency id the greatest, they produce the moit objectionable
glare effects. The light distribution on the working plane
is by far better with the Alba reflectors. Un this case

-S4.

the distribution is alnost ideal, while^ the light
distribution due to the Holophane reflectors is very
uneven, as is well shown by the res^pective distribution
curves. Economically the Holophane reflectors have a
decided advantage over the Albas, physiologically they
are at a great disadvantage. We do not intend ii4»K here
to convey the idea that the' Alba reflectors, when used in
this manner; produce a perfect systen of illumination in
every respect. They have, in fact, some objectionable
features, such as some amount of glare from the bare
incandescent filament of the lamps, but this defect is
more predominating in the Holophane reflectors. As to
the effect that the two types of reflectors produce on
the observer, there is no great difference.. Aesthetically

they are both pretty.

are placed
When the three types of refleclorsAon the fixtures

^isssi (i»n the four quarter bays, the X Ray reflectors

acting as a totally indirect system of illumination, and

the Alba and Holophane reflectors acting as semi-indirect

systems, the comparison is again in favor of the Alba

-3S.

reflectors. We may peremptorily discard the Holophane
reflectors from this group, as being the lowest in effi-
ciency and physiologically objectionable* As between the
Alba and the X Ray reflectors, the 4ait«-r are to be
preferred; for no other reason than that of higher effi-
ciency. The appearance of the room, lighted with the Alba
reflectors, is a little more cheerfpl than when it is
lighted with the Holophane or X Ray reflectors.

O O O 0|^0 o o o

The following general conclusions may be drawn as the
result of this research?

From the point of view of illuminating efficiency,
the Holophane reflector is more desirable than the other
types of illuminating units. This good point is, however
completely offset by the predominance of glare. The X Ray
reflectors, if used at all, should be used distributed in
the four quarter bays,, and should be provided with lamps
of a higher rating than 1'50 watts. These reflectors lose
much of their worth if dust is allowed to accumulate on

36

their polished surface, consequently their cost of
maintenance is considerably higher than any of the other
two types of reflectors. The Alba reflectors give the
best satisfaction under the circumstances. Their effi-
ciency is high, their glare effect is negligible, and they
look good. Preferably they should be used distributed on
the four quarter bay fixtures, turned downwards.

.22.

O O OpjO o o

Calibration of comparison tungsten lamp.

Standard carbon lamp gives 16 C.P. at 116.1 volts.
Voltage impressed d»n comparison lamp = 110.5 volts.
Distance of photometer screen from standard lamp = 40 cm.
" " " " " "- comparison " = 50 cm.

13 ^ 50
C.P. of comparison lamp = -- — -r^ = 25

40^

__IABLI_II-,

O O Op,0 o o

Calibration of lamp # 1
Voltage impressed on comparison lamp = 110.5 volts.
Voltage impressed on cervics lamp = HO volts.
Distance o(ff standard lamp from screen = 50 cms.
Distance of service lamp from screen = D,S. cms.
Horizontal angle through which lamp was turned = 6

0

30°
30"
90°
Average distance of lamp from screen = 104.3 cms.

C.P. of lamp = _25_2i_104^^ = 109

50^
Reduction factor of lamp = . 79

M.S. C.P. = .79 X 109 = 86.11

Total lumens emitted by lamp = 4 x 3.14 x 38.11 = 1082.5

Current in lamp = li32 amps..

1082.5
Observed lumens per watt = = 7.47

110 X 1.32

D.S.

t

D.S.

0

D.S.

103

120°

104.2

240°

105 ..4

102.8

150°

104^3

270°

105.8

102.5

180°

104.5

300°

105 ..0

104.1

210°

105.5

330°

104.8

-32-

O O OoO o o

Calibration of Lamp # 2

Voltage impressed on comparison lamp = 110.5 volts

voltage impressed on service lamp =■ HO vol^s.

Distance of standard lamp from screen = 50 cms.

Distance of service lamp from screen = D.S. cms.

Horizontal angle throjigh which the lamp was turned=lZli''

iZ) D.S. t D.S. t D.S.

0 107.4 120° 105.5 240° 106.0

30° 106.5 150° 1D6.0 270° 108.5

60° ^5.8 180° 108.7 300° 103.9

90° 106.5 210° 106.0 330° 108.7

average distance of lamp from screen = 107 cms.

25 » 107^ _^ ^
Horizontal candle power of lamp = = 114, o

50^
Reduction factar of lamp = .79

Mean spherical candle power = .79 ■*■ 114.5 = 90.5

Total lumens emitteti by lamp = 4 x 3.14 x 90.5 - 1140

Current in lamp = 1.47 amps.

^140 _,_.
Lumens per watt = ~7Tf)~x~T~47 — ~

-4Q.

o o o r\0 o o

Calibration of Lamp # 3
Voltage impressed on comparison lamp = 110.5 volts.
Voltage impressed on service lamp = = 110 volts.
Distance of standard lamp from screen ■ 50 cms.
Bistance of srevice lamp from screen = D.S. cms.
Horizontal angle through wnich lamp was turnad = 6

6

D.S.

i)

D.S.

Ifi

D.S.

0

165.5

120°

104.3

240°

103.0

30°

105.0

150°

104°7

270°

104.2

60°

105.5

130°

105.0

300°

104.0

90°

101.5

210°

105.0

330°

103.3

Ave8«ge distance of lamp from screen = 104.3 C91S.

25 ^ 104.32
Mean horizontal candle power = = 109

50^

Reduction factor of lamp = .79

Mean spherical candle power = .79 " 109 = 36.11

Total lumens emitted by lamp = 4 x 3.14 " 85.11 - 1083.5

Current in lamp = 1,37 amps.

1082.5
Lumens per watt = -------j--- =7.2

41

o o o aO o o

Calibration of Lamp # 4
Voltage impressed on comparisdin lamp = 110.5 volts
Voltage impressed on service lamp =• 110 volts
Distance of standard lamp from screen = 50 cms.
Distance of service lamp from screen = D.S, cms.
Horizontal angle through which lamp was turned = 2)
25 D.S. 25 D.S.
120° 136.0 240° 103.2
150° 106.4 270° 106.5
180° 103.7 300° 106.7
210° 103.7 330° 103.0

Average distance of lamp from screen = 105 cms.

25 X 105^
Mean horizontal candle power = ' — = 110.5

50^

Reduction factor of lamp = .79

Mean spherical candle power = ,79x110.5 = 87.3

Tojal lumens emitted by lamp = 4x3,14x87.3 = 1100

Current in lamp * 1.325 amps.

1100

Lumens per watt = t-t;?;--.-^;^ ~ 7,55

1.325xL10

Z5

D.S.

0

104.4

30°

105°0

60°

104.5

90°

106.4

_i2_

Four E-lOO, National X Ray reflectors, in center of

room, equipped with 150 watts tungsten lamps.

Distance of edge of reflectors from ceiling = 2 ft.

Lamps voltgge " 110 volts.

Lamps current = 5.45 amps.

Photometer millivoltmeter reading = .922

Sta. F.C. Int. Sta. F.C. Int. Sta. F.C. Int,

1 3.49 11 2.80 21 1.68

2 3.15 12 2.59 22 1.55

3 2.80 13 2.30 23 1.35

4 2.18 14 1.83 24 1.15

5 1.70 15 1.50 25 1.02

6 1.60 16 1.23 26 .71

7 2.03 17 1.45 27 .33

8 2.60 18 1.70 28 i.oo

9 2.96 19 2.10 29 1.12
10 3.27 20 2.17 30 1.15

Avesage F.C. intensity = 1.90

43

OOO/^OOO

'0'
Fojir E-lOO, National X Ray reflectors, in center of

room, equipped with 150 watts tungsten lamps.

Distance of edge of reflectors from ceiling = 3 ft.

Lzmps voltage = 1:10 volts.

Lamps current = 5.43 amps.

Photometer millivoltmeter reading = .922

Sta.

F.C. Int.

Sta.

F.C. Int.

Sta.

F.C. Int

1

3.40

11

2.87

21

1.63

2

3.13

12

2.54

22

1.60

3

2.75

13

2.22

23

1.38

4

2.25

14

1.82

24

1.22

5

1.80

15

1.42

25

1.03

6

1.64

16

1.17

26

76

7

2.10

17

1.50

27

.91

8

2.67

18

1.35

28

1.06

9

3.00

19

2.08

29

1.17

1§0

3.25

20

2.22

30

1.25

Average F.C. intensity = 1.92

-44.

O O O r\0 O O

Four E-lOO, National X Ray reflectors, in center of

room, equipped with 150 watts tungsten lamps.

Distance of edge of reflectors from ceiling = 4 ft.

Lamps voltage = 110 volts.

Lamps current = 5.45 amps.

Photometer millivoltmeter reading = .922

o o o^o o o

Sta.

F.C.Int.

Sta.

F.C. Int.

Sta.

F.C. Int

1

3.22

11

2.73

21

1.70

2

3.02

12

2.55

22

1.63

3

2.67

13

2.23

23

1.43

4

2.25

14

1.73

24

1.18

5

1.77

15

1.39

25

.99

6

1.60

16

1.20

26

.79

7

2.02

17

1.51

27

.92

8

2.42

18

1.82

28

1.97

9

2.90

19

2.05

29

1.18

19

3.00

20

2.22

30

1.23

Average F.C. intensity = 1.91

45

o o o r\0 o o

•0'

Four E-IDO, National X Ray reflectors, in center of rooir
equipped with 150 watts tungsten lamps.
Distance of edge of reflectors from ceiling = 5 ft.
Lamps voltage " 110 volts.
Lamps current = 5,45 amps.
Photometer roillivoltmeter reading =• .922

oo

I o^o oo

Sta.

F.C. Int.

sta.

F.C. Int.

Sta.

•F.C. Ii

1

3.00

11

2.55

21

1.65

2

2.90

12

2.35

22

1.56

3

2.45

13

2.10

23

1.88

4

2.05

14

1.78

24

1.20

5

1.67

15

1.38

25

. 98

6

1 .55

16

1.20

26

.78

7

2.00

17

1.52

27

.92

8

2.35

18

1.77

28

1.03

9

2.60

19

2.00

29

1.17

10

2.a(

20

2.15

30

1.23

Average F.C. intensity = 1.80

-4S.

Four E-lOO National X Ray reflectors, equipped with

150 watts tungsten lamps, distributed in corners.

Distance of edge of reflectors from ceiling = 3 ft.

Lamps voltage = 110 volts.

Lamps current = 5.45 Amps,

Photometer millivoltmeter reading = .922

o o o ^o o o

Sta.

F.C. Int.

Sta.

F.C. Int.

Sta.

F.C. Int

1

2.30

11

2.18

21

1.95

2

2.30

12

2.22

32

1.88

3

2.20

13

2.10

23

1.77

4

2.05

14

1.94

24

1.65

5

1.78

15

1.68

25

1.43

6

1.70

16

1.54

26

1.16

7

1.95

17

1.85

27

1.20

S

2.10

18

2.00

23

1.51

9

2.20

19

2.10

29

1.58

10

2.30

20

£.13

30

1.54

Average F.C. Intensity =5^ l.l

-42-

-IAEL£— XI—

O O CxO o o

Four E-lOO, National X Bay reflectors, equipped with

150 watts tungsten lamps, distributed in bays.

Distance of edge of reflectors from ceiling = 3 ftr

Lamps voltage = HO v,atlts

Lamps current = 5.43 amps.

Photometer millivoltmeter reading = . 94

O O O r\0 O O

Sta.

F.C. Int.

Sta.

F.C. Int.

Sta.

F.C. Ii

1

2.32

11

2.15

21

1.90

2

2.30

12

2.15

22

1.80

3

2.25

13

2.03

23

1.73

4

. 2.05

14

1.92

24

1.60

5

1.80

15

1.65

25

1.40

6

1.80

16

1.50

26

1.12

7

2.05

17

1.78

27

1.26

3

2.22

18

2.00

28

1.45

9

2.30

19

2.10

29

1.55

10

2.30

20

2.10

30

1.55

Average F.C. intensity - 1.87

-42-

O O O f\0 o o

Four E-lOO National X Ray reflectors, equipped with

150 watts tungsten lamps, distributed in bays.

Distance of edge of reflectors from ceiling = 4 ft.

Lamps voltage " 110 volts.

Lamps current ■ 5.44. amps.

Photometer roillivoltmeter reading " ..94

oo

0|^0 o o

Sta.

F.C. Int.

sta.

F.C. Int.

Sta.

F.C. Int.

1

2.43

U

2.25

21

1.80

2

2.39

12

2.10

22

1.73

3

2.23

13

2.00

23

1.66

4 .

2.10

14

1.90

24

1.54

5

1.80

15

1.57

25

1.33

6

1.77

16

1.45

26

1.07

7

2.12

17

1.71

27

1.25

8

2.30

13

1.90

28

1.42

9

2.35

19

2.10

29

1.47

10

2.40

20

2.12

30

1.55

Average F.C. intensity = 1.86

-49.

O O O r\0 OO

Four 5^3445 Alba reflectors, equipped with 150 watts

tungsten lamps, in center of room, turned upwards.

Distance of edges of reflectors from ceiling = 3 ft.

Lamps voltage = 110 volts.

Lamps current = 5.45 amfis.

Photometer millivoltmeter reading = ,94

O o O r\0 o o

Sta,

F.C. Int.

Sta.

F.C. Int.

Sta.

F.C. Int

1

5.90

11

4.10

21

2.05

2

5.03

12

3.65

22

1.94

3

4.10

13

3.00

23

1.80

4

3.10

14

2.55

24

1.54

5

2.40

15

1.93

25

1.32

6

2.25

16

1,49

26

1.05

7

2.90

17

1.87

27

1.17

8

3.77

13

2.20

23

1.37

9

4.55

19

2.63

29

1.48

10

5.10

20

2,83

30

1.60

Average F.C. intensity = 2.70

lASLE-KU-

O O O r\0 O O

Four #3445 Alba reflectors, equipped with 150 watts

tungsten lamps, in center of roon, turned upwards.

Distance of edge of reflectors from ceiling = 4 ft.

Lamps voltage = 110 volts.

Lamps current = 5.45 amps.

Photometer raillivoltmeter reading = .94

o o c

> f\00 o

Sta.

F.C. Int.

sta.

F.C. Int.

Sta.

F.C. Int

1

3.55

U

4.14

21

2.05

2

5.45

12

3.65

22

1.95

3

4.22

13

3.08

23

1.80

4

3.03

14

2.47

24

1.49

5

2.43

15

2.05

25

1.87

3

2.23

IS

1.53

23

1.00

7

2.90

17

1.93

27

1.17

3

3.70

13

2.33

23

1.38

9

4.75

19

2.67

29

1.45

10

5.85

20

2.84

30

1.80

Average F.C. intensity = 2.37

-51_

O O O r\0 O O

Four #3445 Alba reflectors, equipped with 150 watts

tungsten lamps, in center of room, turned upvi'ards.

Distance of edge of reflectors from ceiling = 5 ft.

Lamps voltage = HO vd»lts.

Lamps current = 5,45 amps.

Photometer tiillivoltaieter reading = .94

O O O /-jO o o

Sta.

F.C. Int.

Sta.

F.C. Int.

Sta.

F.C. int

1

7.80

11

4.20

21

2.96

2

5.80

12

3.65

22

1.95

3

4.30

13

3.10

23

1.75

4

4.00

14

2.37

24

1.46

5

2.42

15

1.82

25

1.85

6

2.22

16

1.54

26

.98

7

2.90

17

1.95

27

1.17

8

3.70

18

2.38

23

1.38

9

4.85

19

2.70

29

1.45

10

5.90

20

2.94

30

1.60

Aveaage F.C. intensity = 2.83

Four #3445 Alba reflectors, equipped with 150 watts

tungsten lamps, distributed in bays, direct lighting.

Distance of edge of reflectors from ceiling = 3 ft. 8 in,

Lamps voltage = 110 volts.

Lamps current = 5.45 amps.

Photometer milllvoltaieter reading = . '94

O O O rsO O O

.Q«

Sta.

F.C. Int.

Sta.

1

3.25

11

2

3.30

12

3

3.20

1-3

4

2.90

14

5

2.30

15

6

2.70

16

7

3.10

17

3

3.30

13

9

3.30

19

10

3.30

20

F.C. Int. Sta. F.C. Int.
3.30 21 2.60
2.70
2.70
2.60
2.13
1.72
2.00-
2.13
2.19
2.15

3.30

22

3.35

23

3.35

24

2.70

25

2.50

26

3.25

27

3.15

28

3.03

29

3.05

30

Average F.C. intensity = 2.83

-53.

Four #3445 Alba reflectors, equipped v»ith 150 watis

tungsten lamps, distributed in bays, direct lighting.

Distance of edge of reflectors from ceiling = 4 ft. 3 in.

Laiii|)s Voltage = 110 volts.

Laqaps current = 5.45 Amps.

Photometer millivoltmeter reading = .94

oo e

,QOoo

Sta.

F.C. Int.

Sta.

F.C. Int.

Sta.

F.C. Int.

1

3.35

11

3.30

21

2.70

2

3.25

12

3.45

22

2.80

3

3.25

13

3.45

23

2.80

4

3.00

14

3.30

24

2.80

5

2.55 ,

15

2.75

25

2.20

6

2.30

13

2.35

23

1.38

7

3.13

17

3.40

27

1.95

8

3.35

13

3.35

28

2.20

9

3.35

Id

3.35

29

2.10

10

3.40

20

3.15

30

2.15

Aveaage F.C. intensity = 2.97

54

o o o r\0 o o

Four ^'3445 Alba reflectors, equipped with 150 watts

tungsten lamps, distributed in bays, direct lighting.

Distance of edge of reflectors from ceiling = 5 ft. 8 in.

Lamps voltage = 110 volts.

Lamps current = 5.45 amps.

Photometer millivoltmeter reading = .94

O O (

'0"

1 o o

Sta.

F.C. Int.

Sta,

.

F

.0, Int.

Sta.

F.C. Int.

1

3.20

11

3.40

21

2.90

2

3.30

12

3.85

22

3.00

3

,3.30

13

3.90 ■

23

3.20

4

3.10

14

3.85

24

2.90

5

2.70

15

2.35

25

2.30

6

2. -80

16

2.70

26

1.65

7

3.20

17

3.80

27

2.05

8

3.43 •

18

3.50

23

2.30

9

3.50

19

3.80

29

2.25

10

3.25

20

3.30

30

2.13

Average

F.C, intansi

ty =

3.

,04

_5§.

OO O r\00 O

Four #3445 Alba reflectors, equipped \vith 150 watts

tungsten lamps, distributed in bays, turned upwards.

Distance of edge of reflectors from ceiling =° 2 ft»

Lamps voltage = tlO volts.

Lamps currant = 5.45 amps.

Photometer tnillivoltmeter reading = .94

O O O r\0 O O

Sta.

F.C. Int.

Sta.

F,

.C. Int.

Sta.

F.C. Int

1

2.70

11

2.70

21

2.25

2

2.70

12

2.70

22

2.30

3

2.65

13

2.68

23

2.13

4

2.50

14

2.47

24

2.05

5

2.20

15

2.12

25

1.78

6

2.18

16

2.02

26

1.47

7

2.50

17

2.40

27

1.68

8

2.80

13

2.68

28

1.83

9

2.70

19

2.70

29

1.35

10

2.30

20

2.58

30

1.38

Average

F.C. intena

iity = 2.

,33

-52,

0 O O ,'\ o o o

Four #3445 Alba reflectors, equipped with 150 watts

tungsten lamps, distributed in corners, turned upwards,

Distance of edge of reflectors ffom' ceiling = 3 ft.

Lamps voltage = 110 volts.

Lamps current = 5.45 amps.

Photometer millivoltmeter receding = .94

o oc

> r> 0 0 0

Sta.

F.C. Int.

sta.

F.G. Int.

STa.

F.G. Int

1

2.80_

11

2.75

21

2.30

2

2.72

IS

2.78

22

2.28

3

2.65

13

2.75

23

2.22

4

2.63

14

2.60

24

2.08

5

2.25

15

2.23

25

1.79

6

2.25

16

2.05

26

1.47

.7

2.50

17

2.45

27

1.73

3

2.63

18

2.67

28

1.89

9

2.73

19

2.64

29

1.92

10

2.75

20 .

2.64

30

1.87

Average F.G. intensity = 2.37

57

ooo r\0 o o

Four #3445 Alba reflectors, equipped with 150 watts

tungsten lamps, distributed in bays, turned upwards,

Distance of edge of reflectors from ceiling = 4 ft.

Lamps voltage = 110 volts.

Lamps current =5.45

Photometer millivoltmeter reading = .94

O 0 c

,QOOO

Sta.

F.C. Int.

Sta.

F.C. Int.

Sta.

F.C. Int

1

2.85

11

2.80

21

2.35

2

2.85

12

2.82

22

2.30

3

2.90

13

2.34

23

2.30

4

2.80

14

2.68

24

2.20

5

3.30

15

2.25

25

T.82

6

2.30

16

2.10

26

1.50

7

2.65

17

2.60

27

1.75

8

2.80

18

2.86

23

1.92

9

2.77

19

2.76

29

1.95

10

2.82

20

2.68

30

1.90

Average F.C. intensity = 2..4f

-52.

o o o ^o o o

Four F-150, S.F., Holophane reflectors, equipped i»ith

150 watts tungsten lamps, in center of room, turned

upwards, serai-indirect lighting.

Distance of edge of reflectors froiti ceiling " 3 ft.

Lamps voltage = 110 volts.

Lamps current =5.42 amps.

Photometer millivoltmeter reading = .94

O O O r\0 O O

Sta.

F.O.. Int.

Sta.

F.C. Int.

Sta.

F.C. Int

1

3.90

11

3.55

21

2.10

2

3.65

12

3.15

22

1.98

3

3.35

13

2.65

23

1.80

4

2.80

14

2.25

24

1.50

5

2.20

15

1.80

25

1.25

6

2.05

16

1.48

25

1.03

7

2.50

17

1.90

27

1.18

3

3.00

18

2.25

23

1.35

9

3.43

19

2.65

29

1.50

10

3.30

20

2.89

30

1.52

Average F.C. intensity = 2.35

-59.

o o 0r\O o o

Four F-150, S.F. Holophane reflectors, equipped with

150 watts tungsten lamps, in center of room, turned

upwards, semi-indirect lighting.

Distance of edge of reflectors from ceiling = 4 ft.

Lamps voltage " 110 volts.

Lamps current = 5.42 amps.

Photonoeter millivollmeter reading = .94

0 0 c

> f\0 o o

Sta.

F.G. Int.

Sta.

F.G. Int.

Sta.

F.C. Int

1

4.00

11

3.50

21

1.95

2

3.90

12

3.10

22

1.90

3

3.45

13

2.65

23

1.70

4

2.80

14

2.13

24

1.43

5

2.20

15

1.75

25

1.24

6

2.05

16

1.45

26

.98

7

2.60

17

1.35

27

1.15

8

3.15

18

2.25

23

1.30

9

3.55

19

2.58

29

1.38

10

3.95

20

2.68

30

1.45

Average F.C. intensity = 2.37

60

o o o .^ o o o

'0'

Four F-150, S.F. Holophane reflectors, equipped with
150 watts tungsten lamps, in center of roofo, timed
upwards, semi-indirect lighting.

Distance of edge of reflectors from (the ceiling - 5 ft,
Lamps voltage = 110 volts.
Lamps current = 5.42 amps.
Photometer millivoltmeter reading = .94

O O O r\00 O

Sta.

F.C. Int.

Sta.

F.C. Int.

Bta.

F.C. Int

1

4.10

11

3.45

21

1.90

2

3.90

12

3.10

22

1.83

3

3.50

13

2.85

23

1.66

4

2.80

14

2.15

24

1.44

5

2.20

15

1.72

25

1.23

6

2.05

16

1.42

26

.94

7

2.60

17

1.32

27

1.12

8

3.20

13

2.25

23

1.23

g

3.60

19

2.55

29

1.30

10

4.00

20

2.30

30

1.37

Average F.C. intensity = 2.32

61

O O O r\0 O O

Four F-150, S.F. Holophane raf lectors, equipped with

150 watts tungsten lamps, Distributed in bays, direct

lighting.

Distance of edge of reflectors from ceiling = 3 ft. 9 in.

Lamps voltage = 110 volts.

Lamps current = 5.43 amps.

Photometer millivoltmeter reading = .94

O O 0^0 o o

Sta. F.C. Int. Sta. F.C. Int. Sta. F.C. Int.

1 3.10 11 3.10 21 2.50

2 2.90 12 3.85 22 2.80

3 2.90 13 4.50 23 3.10

4 2.75 14 4.00 24 2.70

5 2.20 15 2.80 25 2. 18

6 2.55 1^ 2.65 26 1.57

7 3.27 17 3.75 27 1.33

8 3.60 18 4.30 28 2.00

9 3.35 19 3.70 29 I.93
13 3.10 20 3.10 30 1.85
Average F.C. Intensity = 2.93

-32-

'0'

four F-150, S.F. Holophane reflectors, equipped with
150 watts tungsten lamps, distributed in bays, direct
lighting.

Distance of edge of reflectors from ceiling = 4 ft. 8 in,
Lamps voltage = HO volts.
Lamps current = 5.48 amps.
Photometer millivoltmeter reading = .94

O 0 O /> O O 0

Sta.

F.C. Int.

sta.

F.O. Int.

Sta.

F.C. Int.

1

2.70

11

3.25

21

2.55

2

2.70

12

4.10

32

3.00

3

2.70

13

4.90

23

3.30

4

2.43

14

4.25

24

2.90

5

2.15

15

2.65

23

2.10

6

2.45

IS

2.65

23

1.50

7

3.25

17

4.20

27

1.32

8

3.60

18

5.00

29

2.05

9

3.35

19

4.00

29

1.95

10

3.00

20

3.20

30

1.85

Average F.C. intensity = 2..99

_63.
• lAELE mil

Four F-150, S.F. Holophane reflectors, equipped with

150 watts tungsten lamps, distributed in bays, direct

lighting.

Distance 6f reflectors from ceiling = 5 ft. 8 in.

Lamps voltage = 110 volts.

Lamps current = 5.42 amps.

Photometer millivoltmeter reading. " .94

o o

o^o o o

Sta.

F.C. Int.

sta.

F.C. Int.

Sta.

F.C. Int.

1

2° 75

11

3.25

21

2.40

2

2.90

12

4.55

22

2.85

3

3.00

13

6.60

23

3.35

4

2.60

14

5.20

24

2.90

5

2.30

15

3.10

25

2.05

6

2.60

16

2.90

26

1.50

7

3. SO

17

4.55

27

1.60

8

4.00

18

5.90

28

1.85

9

3.35

19

4.20

29

1.77

10

2.90

20

3.O0

30

1.72

Average F.C. intensity = 3.17

Four F-150, S.F. Holophane reflectors, equipped with

150 watts tungsten lamps. Bistributed in bays, turned

upwe|,rds.

Distance of edge of reflectors frota ceiling = 2 ft.

Lamps voltage = 110 volts

Lamps current = 5,45 amps.

Photometer millivoltraeter reading =.94

o o <

0|^O o o

Sta.

F.C. Int.

sta.

F.C. Int.

Sta.

F.C. Int.

1

2.30

11

2.20

21

1.96

2

2.30

12

2.10

22

1.82

3

2.15

13

1.92

23

1.78

4

1.94

14

1.79

24

1.65

5

1.73

15

1.62

25

1.48

6

1.74

16

1.51

26

1.25

7

1.95

17

1.69

27

1.35

8

2.10

18

1.80

23

1.49

9

2.25

19

2.00

29

1.50

10

2.30

20

2.02

30

1.50

Average F.C. intensity = 1.83

o o or\0 o o

Four F-150, S.F. Holophane reflectors, equipped with

150 watts tungsten lamps, distributed in bays, turned

upwards.

Distance of edge of reflectors from ceiling = 3 ft.

Lamps voltage = 110 volts.

Lzmps current = 5.45 amps.

Photometer millivoltmeter reading '^ .94

OO'

0/->OOO

Sta.

F.C. Int.

sta.

F.O. Int.

Sta.

F.C.. Int.

1

2.30

11

2.20

21

1.81

2

2.20

12

2.12

22

1.79

3

2.17

13

1.35

23

1.71

4

1.98

14

1.79

24

1.61

5

1.73

15

1.65

25

1.45

6

1.77

16

1.55

26

1.20

7

1.96

17

1.76

27

1.35

8

2.10

18

1.78

23

1.52

9

2.22

19

2.00

29

1.54

10

2.30

20

2.07

30

1.54

Average F.C. Intensity = 1.83

-22-

O O O r\0 O O

Four F-150, S.F. Holophane reflectors, equipped with

150 watts tungsten lamps, distributed in bays, turned

upwards.

Distance of edge of reflectors from ceiling = 4 ft.

Lamps voltage = 110 volts.

Lamps current = 5.45 amps.

Photometer mi Hi voltmeter reading = .94

0 0 0 p.0 o o

Sta.

F.C. Int.

Sta.

F.C. Int.

Sta.

F.C. In

1

2.25

11

2.18

21

2.00

2

2.20

12

2.18

22

1.70

3

2.10

13

1.82

23

1.69

4

1.83

14

1.92

24

1.59

5

1.76

15

1.66

25

1.43

6

1.75

16

1.52

26

1.21

7

1.99

17

1.72

27

1.34

8

2.10

13

1.74

28

1.50

9

2.21

19

2.03

29

1.52

10

2.28

20

2.13

30

1.53

Average F.C. intensity = 1.83

.52-

-TAELE.Xni.

O O Op.O o o

Operating characteristics of four E-lOO Natioaal X Ray
reflectors, equipped vvith 150 watts tungsten lamps, placed
in a room 27.5 ft. long, 23 ft. wide, and' 14.5 ft. high.

1
roi

■•->

CO

CI

■«

c^

V 1

oa

o

E 1 m

St

■H

>»

31 C

o

-M

f-H 1 1)

C<

v>

•rt

1 e

1)

r-)

CO

m

05

1 3

Q.

««H

c

c

a

1. <»-<

•u

■D

V

V

O f

.

C

+J

e

e

V f •

B

■Qt

C

a

a

Vh ! C

3

<M

C

•^

nH

r— t

<t-i t Ti

rH

o

■ rH

ta lo

.-<

.

1)

Tf

I

■u

n

•rH

c:)

>

V

1

>

o

1)

•tH

-U

•iH

c

o

u,

+J

*

II

4->

<j3

o

Sj

o

-M

a

c

1)

T)

.

•1>

m

o

c8

Vh

C

Vh

tw

•(H

t^

1>

t«-i

V

«^^

tt-<

_j:a.

-«!=<..

S

— &a.—

-X2-

_ja

&a

Reflectors on

2

1.90

1200

4405

.278

2.00

center fixture

3

1.92

1215

4405

.273

2.02

4

1.91

1207

4405

.275

2.01

5

1.80

1140

4405

.258

1.90

Reflectors

2

1.88

1190

4405

.270

1.98

distributed in

3

1.87

1188

4405

.270

1.97,

four bays.

4

1.88

1186

4405

.270

1.93

o o o p,o o o

Operating characteristics of four #3445 Alba reflectors

equipped with 150 watts tungsten lamps, placed in a

room 27.5 ft. long, 23 ft. wide, and 14.5 ft. high.

>, • I

05 -tJ ■4J B I

O no 05 05 rH ' B +->

+J C C C C 1 3 -|J

O •-< 15 1) T> • Ic— I £l1

V +^ S SO' S

,— (yali C t3 n •i>'.~^

;*-.C -rH rH r-4 t^nlC •

U. ^ . 15 T-) &a-tO :3

.r-i c:) > "U I ■-•

«n 15 • — < +^

O O Cti -t-" "tl II •

O '-I t5

.6 a 15 15 • 1>

05 O cfl «w C t-i =<-i

.,H t-4 1) «*-" 1) '^ '^

ca «M :^ Cd o Ed &u

Reflectors in 3 2-70 1710 4405 .387 2.85

(kenter fixture 4 2.7Q 1740 4405 .395 2.92

5 2.83 1790 4405 .406 2.93

turned upwards

Reflectors 3.75 2.83 1790 4405 .408 2.98

distributed in 4^75 2.97 1380 4405 .426 3.14

four bays

direct lighting 5.75 3.04 1920 4405 .436 3.20

Reflectors 2. 2.33 1470 4405 .334 2.45

distributed in 3 2.37 1500 4405 .340 2.50

four bays

turned upwards ^ 2.45 1550 4405 .352 2.58

o o o ao o o

Operating characteriatics of four F-150, S.F. Holophane
reflectors, equipped with 150 watts tungsten lamps, placed
in a room 27.5 ft. long, 23 ft, wide,andl4.5 ft. high.

o

•

C I

ert

+j

-u

>»

V 1 TO

s

o

V-1

+j

etc

V

•H

D 1 1)

t.

rH

c

m

CD

a>

rH 1 e

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tn

>pH

c

C

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V

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U,

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3

D 1 .

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V

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c

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ffi

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Vh

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t^

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=t-c

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Vh

«.-i

o_

Vh

^

-_¥--

Cp^^

&i_

fei

Reflectors on

3

2.35

1485

4405

.337

2.47

center fixture

4

2.37

1500

4405

.340

2.50

turned upwards

5

2.32

1468

4405

.333

2.44

Reflectors

3.

75

2.93

1358

4405

.420

3.03

distributed in

4.

75

2.99

1390

4405

.429

3.15

four bays

direct lighting

5.

75

3.17

2000

4405

.453

3.33

Reflectors

2

1.83

1165

4405

.263

1.93

distributed in

3

1.83

11S5

4405

.233

1.93

four bays

turned upwards

4

1.83

1165

4405

.263

1.93

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